In general, conventional ring spinning requires a number of preparatory steps in the manufacturing of spun yarns of synthetic fibers. Disadvantages of the conventional process are low productivity, nep formation and increasing irregularity in weight per length in the opening and drafting stages. Therefore, the conventional ring spinning requires redundant steps in addition to the indispensable steps. Further, even the complicated steps of the conventional process, it is very difficult to form fibers of poor physical properties, such as fibers of cured novolac resin or cured novolacpolyamide resin, into yarns. In manufacturing spun yarns of textile fibers, for example, polyester fibers, polyamide fibers and polyacrylic fibers, conventional ring spinning requires a restriction on the diameter of supplied staple fiber. Thus, it is very difficult to manufacture spun yarns made of fibers of fine denier.
Much research effort has been directed and many methods have been proposed to remove these defects of the conventional ring spinning, as shown in U.S. Pat. No. 3,079,746, U.S. Pat. No. 3,365,872 and British Pat. No. 1,102,095.
U.S. Pat. Nos. 3,079,746 and 3,365,872 disclose the manufacture of spun yarns made of discontinuous fibers or a combination of discontinuous fibers with continuous strands. However, since these patents are confined to only improvements in the twisting step, many of the preparatory steps for making slivers in the ring spinning process still need to be improved.
British Pat. No. 1,102,095 discloses a product and a process wherein some qualities characteristic of a spun staple fiber yarn are imparted to continuous filamentary yarn. Such yarns are apt to have many long radially-projecting loops. However, the presence of these radially-projecting loops, particularly the presence of long loops on the surface of the yarns, imparts undesirable properties to the yarn. For instance, in knitting fabrics, long loops induce irregular tension when the yarn is unwound from a cone or a bobbin and cause many defects in the fabrics.